CATransaction completion being called immediately

Question

I'm trying to execute a completion-block after my CAAnimation has finished. However, it seems that animation block is called before my animation completes. The animation still happens correctly though.

[CATransaction begin];
[self.view.layer addAnimation:self.dropAndBounceAnimation forKey:@"appearance"];
[CATransaction setCompletionBlock:completionBlock];
[CATransaction commit];

The dropAndBounceAnimation is a CAKeyFrameAnimation on position.y, with a fixed duration.

Answer 1

I'm not sure if this really is the correct fix, but by setting the completion-block before adding the animation for the layer, the completion-block is consistently called at the correct time.

[CATransaction begin];
[CATransaction setCompletionBlock:completionBlock];
[self.view.layer addAnimation:self.dropAndBounceAnimation forKey:@"appearance"];
[CATransaction commit];

Answer 2

You need to set the completion block before adding the animation.

[CATransaction begin];
[CATransaction setValue:[NSNumber numberWithFloat: 1.0f] forKey:kCATransactionAnimationDuration];

[CATransaction setCompletionBlock:^{
// ... whatever you want to do when the animation is complete
}];

[self.googleMapsView animateToCameraPosition:[GMSCameraPosition 
                    cameraWithLatitude:LATITUDE
                             longitude:LONGITUDE
                                  zoom:ZOOM]];

[CATransaction commit];

This must trigger the completion block after the completion of that animation on the view.

Answer 3

Here is Swift 3.0.1, Xcode 8 version:

CATransaction.begin()

CATransaction.setCompletionBlock({
  print("Transaction completed")
})

print("Transaction started")
view.layer.add(dropAndBounceAnimation, forKey: "appearance")

CATransaction.commit()

Answer 4

Try to start the animation asynchronously:

DispatchQueue.main.async {
    self.startAnimation()
}

because it can interfere with view drawing if you make some view setup before calling the animation.